whether the cause of this is happening, is it something to do with the decision of the south korea government?
I agree, I think South Korea government has something to do with bitcoin's sudden price fall but it is only part of it. Most of the government still don't accept bitcoins and other cryptocurrencies and they even want to elimenate or ban them in some countries, so if it would happen then bitcoin's price will fall down and it will become a serious problem for bitcoin users like us.